Within the rapidly advancing field of microbial diagnostics, research and analytical procedures now require analysis at the nucleic acid level to provide the ultimate identification code unique to each specific microbial strain.
Numerous extraction methods have been developed in attempts to efficiently access these nucleic acids. For diagnostic systems entailing the analysis of a variety of unknown microbes, the method of choice must be capable of simultaneously extracting nucleic acids from a range of bacterial types, including both Gram negative and Gram positive bacteria. Further, a useful method must render extracted nucleic acids which are sufficiently intact and in suitable condition for further biochemical analysis and enzymatic characterization.
U.S. Pat. No. 4,900,677 and European Patent Application 87308431.3 (Hewitt) disclose a procedure for isolating high molecular weight nucleic acids utilizing a mixture of lytic enzymes in combination with a chaotropic agent. Unlike the instant invention, the method necessarily entails a dialysis and concentration step to remove enzyme inhibitors before the extracted nucleic acids may be analyzed enzymatically.
International Patent Application No. PCT/US89/0346 (WO90/102179, Lifecodes Corporation) discloses a broad process for isolating DNA from a range of biological samples, including blood cells, semen, urine, tissue, Hela Cells, hair and E. coli. The method states that a separate purification step to remove residual proteolytic activity from lysed cells may be avoided by heating the lysed samples to a temperature and for a time sufficient to autodigest or inactivate residual proteolytic activity. Unlike the instant method, however, this disclosure does not enable a method which has utility in extracting nucleic acids from both Gram negative and Gram positive bacterial strains. Further, in contrast to the instant invention, this disclosure does not demonstrate efficacy in extracting nucleic acids which are suitable for direct enzymatic manipulation in situ.